1. Field of the Invention
The present invention relates to light beam scanning, more particularly, it relates to a method for constructing a hologram having improved interference fringes on a transparent disk, and to a method and apparatus for scanning a light beam during a reconstruction of such a hologram. The present invention is advantageous for use in a laser printer of a computer system.
2. Description of the Prior Art
Recently, laser printers are being widely used as an output apparatus in a computer system, because of their high speed and high-quality printing. These laser printers mainly consist of a laser beam source as a coherent light beam, for example, an He-Ne gas laser or a semiconductor laser, an ultrasonic light modulator, a multi-faceted rotating mirror, an f8 lens, and a drum. However, a printer using these elements, particularly the multi-faceted rotating mirror, requires a highly-complex structure and high precision assembly during manufacture. As a result, a laser printer is very expensive.
Attempts have been made by, for example, Xerox Corporation, Nippon Electric Co., Ltd., and FUJITSU LIMITED, to solve the above-mentioned problems by using a hologram instead of the multi-faceted rotating mirror in the laser printer.
However, although these attempts have achieved a simplified structure and assembly, and also reduce costs, and although they have facilitated laser use in a bar-code reader of a so-called point of sales (POS) system, sufficient precision has not been obtained to enable a hologram to be used in a laser printer, while providing the precision of a conventional multi-faceted rotating mirror. This will be explained in detail hereinafter.